Apparatus and methods for mapping and ablation in electrophysiology procedures

ABSTRACT

An electrophysiology catheter and method of use for mapping and ablation procedures. The catheter includes a braided conductive member at its distal end that can be radially expanded. The catheter can be used in endocardial and epicardial mapping and ablation procedures.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. ProvisionalApplication Serial No. 60/261,015 entitled HIGH DENSITY MAPPING ANDABLATION CATHETER AND METHOD OF USE, filed Jan. 11, 2001; U.S.Provisional Application Serial No. 60/204,457 entitled METHOD FORCREATING ANNULAR EPICARDIAL LESIONS AT THE OSTIA OF THE PULMONARY VEINS,filed on May 16, 2000; U.S. Provisional Application Serial No.60/204,482 entitled METHOD AND DEVICE FOR CREATING ANNULAR ENDOCARDIALLESIONS AT THE OSTIA OF THE PULMONARY VEINS, filed May 16, 2000; andU.S. Provisional Application Serial No. 60/201,445 entitled TRANSMURALCIRCUMFERENTIAL LESIONS MADE AT CANINE PV OSTIUM BY EXPANDABLE MESHELECTRODES IN VIVO, filed May 3, 2000, which applications are herebyincorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The invention relates to medical devices for performing mappingand ablation procedures. More particularly, the invention relates tomethods and apparatus for mapping and ablating at or near the ostia ofthe pulmonary veins or coronary sinus.

[0004] 2. Discussion of the Related Art

[0005] The human heart is a very complex organ, which relies on bothmuscle contraction and electrical impulses to function properly. Theelectrical impulses travel through the heart walls, first through theatria and then the ventricles, causing the corresponding muscle tissuein the atria and ventricles to contract. Thus, the atria contract first,followed by the ventricles. This order is essential for properfunctioning of the heart.

[0006] Over time, the electrical impulses traveling through the heartcan begin to travel in improper directions, thereby causing the heartchambers to contract at improper times. Such a condition is generallytermed a cardiac arrhythmia, and can take many different forms. When thechambers contract at improper times, the amount of blood pumped by theheart decreases, which can result in premature death of the person.

[0007] Techniques have been developed which are used to locate cardiacregions responsible for the cardiac arrhythmia, and also to disable theshort-circuit function of these areas. According to these techniques,electrical energy is applied to a portion of the heart tissue to ablatethat tissue and produce scars which interrupt the reentrant conductionpathways or terminate the focal initiation. The regions to be ablatedare usually first determined by endocardial mapping techniques. Mappingtypically involves percutaneously introducing a catheter having one ormore electrodes into the patient, passing the catheter through a bloodvessel (e.g. the femoral vein or artery) and into an endocardial site(e.g., the atrium or ventricle of the heart), and deliberately inducingan arrhythmia so that a continuous, simultaneous recording can be madewith a multichannel recorder at each of several different endocardialpositions. When an arrythormogenic focus or inappropriate circuit islocated, as indicated in the electrocardiogram recording, it is markedby various imaging or localization means so that cardiac arrhythmiasemanating from that region can be blocked by ablating tissue. Anablation catheter with one or more electrodes can then transmitelectrical energy to the tissue adjacent the electrode to create alesion in the tissue. One or more suitably positioned lesions willtypically create a region of necrotic tissue which serves to disable thepropagation of the errant impulse caused by the arrythromogenic focus.Ablation is carried out by applying energy to the catheter electrodes.The ablation energy can be, for example, RF, DC, ultrasound, microwave,or laser radiation.

[0008] Atrial fibrillation together with atrial flutter are the mostcommon sustained arrhythmias found in clinical practice.

[0009] Current understanding is that atrial fibrillation is frequentlyinitiated by a focal trigger from the orifice of or within one of thepulmonary veins. Though mapping and ablation of these triggers appearsto be curative in patients with paroxysmal atrial fibrillation, thereare a number of limitations to ablating focal triggers via mapping andablating the earliest site of activation with a “point” radiofrequencylesion. One way to circumvent these limitations is to determineprecisely the point of earliest activation. Once the point of earliestactivation is identified, a lesion can be generated to electricallyisolate the trigger with a lesion; firing from within those veins wouldthen be eliminated or unable to reach the body of the atrium, and thuscould not trigger atrial fibrillation.

[0010] Another method to treat focal arrhythmias is to create acontinuous, annular lesion around the ostia (i.e., the openings) ofeither the veins or the arteries leading to or from the atria thus“corralling” the signals emanating from any points distal to the annularlesion. Conventional techniques include applying multiple point sourcesaround the ostia in an effort to create such a continuous lesion. Such atechnique is relatively involved, and requires significant skill andattention from the clinician performing the procedures.

[0011] Another source of arrhythmias may be from reentrant circuits inthe myocardium itself. Such circuits may not necessarily be associatedwith vessel ostia, but may be interrupted by means of ablating tissueeither within the circuit or circumscribing the region of the circuit.It should be noted that a complete ‘fence’ around a circuit or tissueregion is not always required in order to block the propagation of thearrhythmia; in many cases simply increasing the propagation path lengthfor a signal may be sufficient. Conventional means for establishing suchlesion ‘fences’ include a multiplicity of point-by-point lesions,dragging a single electrode across tissue while delivering energy, orcreating an enormous lesion intended to inactivate a substantive volumeof myocardial tissue.

[0012] Commonly-owned U.S. patent application Ser. No. 09/396,502,entitled Apparatus For Creating A Continuous Annular Lesion, which ishereby incorporated by reference, discloses a medical device which iscapable of ablating a continuous ring of tissue around the ostia ofeither veins or arteries leading to or from the atria.

SUMMARY OF THE INVENTION

[0013] The present invention encompasses apparatus and methods formapping electrical activity within the heart. The present invention alsoencompasses methods and apparatus for creating lesions in the hearttissue (ablating) to create a region of necrotic tissue which serves todisable the propagation of errant electrical impulses caused by anarrhythmia.

[0014] In one embodiment, the present invention includes a medicaldevice including a catheter having a braided conductive member at adistal end thereof, a mechanism for expanding the braided conductivemember from an undeployed to a deployed position, and a mechanism forapplying energy via the braided conductive member to blood vessel.

[0015] In one embodiment, the medical device further includes amechanism for irrigating the braided conductive member

[0016] In another embodiment, the medical device further includes atleast one reference electrode disposed on a shaft of the catheter.

[0017] In another embodiment, the medical device includes a mechanismfor controlling the energy supplied to the braided conductive member.

[0018] In another embodiment, the medical device further includes amechanism for covering at least a portion of the braided conductivemember when the braided conductive member is in the deployed position.

[0019] In another embodiment, at least a portion of the braidedconductive member has a coating applied thereto.

[0020] In another embodiment, the medical device includes a mechanismfor measuring temperature.

[0021] In another embodiment, the medical device includes a mechanismfor steering the catheter.

[0022] The invention also includes a method for treating cardiacarrhythmia, including the steps of introducing a catheter having abraided conductive member at a distal end thereof into a blood vessel,expanding the braided conductive member at a selected location in theblood vessel so that the braided conductive member contacts a wall ofthe blood vessel, and applying energy to the wall of the blood vesselvia the braided conductive member to create a lesion in the bloodvessel.

[0023] In another embodiment, the invention includes a method fortreating cardiac arrhythmia, including the steps of introducing acatheter into a thoracic cavity of a patient, the catheter having abraided conductive member at a distal end thereof, contacting anexterior wall of a blood vessel in a vicinity of an ostium with thebraided conductive member, and applying energy to the blood vessel viathe braided conductive member to create a lesion on the exterior wall ofthe blood vessel.

[0024] The braided conductive member may be a wire mesh.

[0025] The features and advantages of the present invention will be morereadily understood and apparent from the following detailed descriptionof the invention, which should be read in conjunction with theaccompanying drawings, and from the claims which are appended at the endof the Detailed Description.

DESCRIPTION OF THE DRAWINGS

[0026] In the drawings, which are incorporated herein by reference andin which like elements have been given like references characters,

[0027]FIG. 1 illustrates an overview of a mapping and ablation cathetersystem in accordance with the present invention;

[0028]FIGS. 2 and 3 illustrate further details of the catheterillustrated in FIG. 1;

[0029] FIGS. 4-7 illustrate further details of the braided conductivemember illustrated in FIGS. 2 and 3;

[0030] FIGS. 8-10A illustrate, among other things, temperature sensingin the present invention;

[0031] FIGS. 11-13 illustrate further details of the steeringcapabilities of the present invention;

[0032] FIGS. 14-17 illustrate further embodiments of the braidedconductive member;

[0033] FIGS. 18-19 illustrate the use of irrigation in connection withthe present invention;

[0034] FIGS. 20A-20E illustrate the use of shrouds in the presentinvention;

[0035]FIG. 21 illustrates a guiding sheath that may be used inconnection with the present invention;

[0036] FIGS. 22-24 illustrate methods of using the present invention.

DETAILED DESCRIPTION

[0037] System Overview

[0038] Reference is now made to FIG. 1, which figure illustrates anoverview of a mapping and ablation catheter system in accordance withthe present invention. The system includes a catheter 10 having a shaftportion 12, a control handle 14, and a connector portion 16. Acontroller 8 is connected to connector portion 16 via cable 6. Ablationenergy generator 4 may be connected to controller 8 via cable 3. Arecording device 2 may be connected to controller 8 via cable 1. Whenused in an ablation application, controller 8 is used to controlablation energy provided by ablation energy generator 4 to catheter 10.When used in a mapping application, controller 8 is used to processsignals coming from catheter 10 and to provide these signals torecording device 2. Although illustrated as separate devices, recordingdevice 2, ablation energy generator 4, and controller 8 could beincorporated into a single device. In one embodiment, controller 8 maybe a QUADRAPULSE RF CONTROLLER™ device available from CR Bard, Inc.,Murray Hill, N.J.

[0039] In this description, various aspects and features of the presentinvention will be described. The various features of the invention arediscussed separately for clarity. One skilled in the art will appreciatethat the features may be selectively combined in a device depending uponthe particular application. Furthermore, any of the various features maybe incorporated in a catheter and associated method of use for eithermapping or ablation procedures.

[0040] Catheter Overview

[0041] Reference is now made to FIGS. 2-7, which figures illustrate oneembodiment of the present invention. The present invention generallyincludes a catheter and method of its use for mapping and ablation inelectrophysiology procedures. Catheter 10 includes a shaft portion 12, acontrol handle 14, and a connector portion 16. When used in mappingapplications, connector portion 16 is used to allow signal wires runningfrom the electrodes at the distal portion of the catheter to beconnected to a device for processing the electrical signals, such as arecording device.

[0042] Catheter 10 may be a steerable device. FIG. 2 illustrates thedistal tip portion 18 being deflected by the mechanism contained withincontrol handle 14. Control handle 14 may include a rotatable thumb wheelwhich can be used by a user to deflect the distal end of the catheter.The thumb wheel (or any other suitable actuating device) is connected toone or more pull wires which extend through shaft portion 12 and areconnected to the distal end 18 of the catheter at an off-axis location,whereby tension applied to one or more of the pull wires causes thedistal portion of the catheter to curve in a predetermined direction ordirections. U.S. Pat. Nos. 5,383,852, 5,462,527, and 5,611,777, whichare hereby incorporated by reference, illustrate various embodiments ofcontrol handle 14 that may be used for steering catheter 10.

[0043] Shaft portion 12 includes a distal tip portion 18, a first stop20 and an inner member 22 connected to the first stop portion 20. Innermember 22 may be a tubular member. Concentrically disposed about innermember 22 is a first sheath 24 and a second sheath 26. Alsoconcentrically disposed about inner member 22 is a braided conductivemember 28 anchored at respective ends 30 and 32 to the first sheath 24and the second sheath 26, respectively.

[0044] In operation, advancing the second sheath 26 distally over innermember 22 causes the first sheath 24 to contact stop 20. Further distaladvancement of the second sheath 26 over inner member 22 causes thebraided conductive member 28 to expand radially to assume variousdiameters and/or a conical shape. FIG. 3 illustrates braided conductivemember 28 in an unexpanded (collapsed or “undeployed”) configuration.FIGS. 2 and 4 illustrate braided conductive member 28 in a partiallyexpanded condition. FIG. 1 illustrates braided conductive member 28radially expanded (“deployed”) to form a disk.

[0045] Alternatively, braided conductive member 28 can be radiallyexpanded by moving inner member 22 proximally with respect to the secondsheath 26.

[0046] As another alternative, inner member 22 and distal tip portion 18may be the same shaft and stop 20 may be removed. In this configuration,sheath 24 moves over the shaft in response to, for example, a mandrelinside shaft 22 and attached to sheath 24 in the manner described, forexample, in U.S. Pat. No. 6,178,354, which is incorporated herein byreference.

[0047] As illustrated particularly in FIGS. 4 and 5 a third sheath 32may be provided. The third sheath serves to protect shaft portion 12 andin particular braided conductive member 28 during manipulation throughthe patient's vasculature. In addition, the third sheath 32 shieldsbraided conductive member 28 from the patient's tissue in the eventablation energy is prematurely delivered to the braided conductivemember 28.

[0048] The respective sheaths 24, 26, and 32 can be advanced andretracted over the inner member 22, which may be a tubular member, inmany different manners. Control handle 14 may be used. U.S. Pat. Nos.5,383,852, 5,462,527, and 5,611,777 illustrate examples of controlhandles that can control sheaths 24, 26, and 32. As described in theseincorporated by reference patents, control handle 14 may include a slideactuator which is axially displaceable relative to the handle. The slideactuator may be connected to one of the sheaths, for example, the secondsheath 26 to control the movement of the sheath 26 relative to innermember 22, to drive braided conductive member 28 between respectivecollapsed and deployed positions, as previously described. Controlhandle 14 may also include a second slide actuator or other mechanismcoupled to the retractable outer sheath 32 to selectively retract thesheath in a proximal direction with respect to the inner member 22.

[0049] Braided conductive member 28 is, in one embodiment of theinvention, a plurality of interlaced, electrically conductive filaments34. Braided conductive member 28 may be a wire mesh. The filaments areflexible and capable of being expanded radially outwardly from innermember 22. The filaments 34 are preferably formed of metallic elementshaving relatively small cross sectional diameters, such that thefilaments can be expanded radially outwardly. The filaments may beround, having a dimension on the order of about 0.001-0.030 inches indiameter. Alternatively, the filaments may be flat, having a thicknesson the order of about 0.001-0.030 inches, and a width on the order ofabout 0.001-0.030 inches. The filaments may be formed of Nitinol typewire. Alternatively, the filaments may include non metallic elementswoven with metallic elements, with the non metallic elements providingsupport to or separation of the metallic elements. A multiplicity ofindividual filaments 34 may be provided in braided conductive member 28,for example up to 300 or more filaments.

[0050] Each of the filaments 34 can be electrically isolated from eachother by an insulation coating. This insulation coating may be, forexample, a polyamide type material. A portion of the insulation on theouter circumferential surface 60 of braided conductive member 28 isremoved. This allows each of the filaments 34 to form an isolatedelectrode, not an electrical contact with any other filament, that maybe used for mapping and ablation. Alternatively, specific filaments maybe permitted to contact each other to form a preselected grouping.

[0051] Each of the filaments 34 is helically wound under compressionabout inner member 22. As a result of this helical construction, uponradial expansion of braided conductive member 28, the portions offilaments 34 that have had the insulation stripped away do not contactadjacent filaments and thus, each filament 34 remains electricallyisolated from every other filament. FIG. 6, in particular, illustrateshow the insulation may be removed from individual filaments 34 whilestill providing isolation between and among the filaments. Asillustrated in FIG. 6, regions 50 illustrate regions, on the outercircumferential surface 60 of braided conductive member 28, where theinsulation has been removed from individual filaments 34. In oneembodiment of the invention, the insulation may be removed from up toone half of the outer facing circumference of each of the individualfilaments 34 while still retaining electrical isolation between each ofthe filaments 34.

[0052] The insulation on each of the filaments 34 that comprise braidedconductive member 28 may be removed about the outer circumferentialsurface 60 of braided conductive member 28 in various ways. For example,one or more circumferential bands may be created along the length ofbraided conductive member 28. Alternatively, individual sectors orquadrants only may have their insulation removed about the circumferenceof braided conductive member 28. Alternatively, only selected filaments34 within braided conductive member 28 may have their circumferentiallyfacing insulation removed. Thus, an almost limitless number ofconfigurations of insulation removal about the outer circumferentialsurface 60 of braided conductive member 28 can be provided dependingupon the mapping and ablation characteristics and techniques that aclinician desires.

[0053] The insulation on each of the filaments 34 may be removed at theouter circumferential surface 60 of braided conductive member 28 in avariety of ways as long as the insulation is maintained betweenfilaments 34 so that filaments 34 remain electrically isolated from eachother.

[0054] The insulation can be removed from the filaments 34 in a varietyof ways to create the stripped portions 50 on braided conductive member28. For example, mechanical means such as abration or scraping may beused. In addition, a water jet, chemical means, or thermal radiationmeans may be used to remove the insulation.

[0055] In one example of insulation removal, braided conductive member28 may be rotated about inner member 22, and a thermal radiation sourcesuch as a laser may be used to direct radiation at a particular pointalong the length of braided conductive member 28. As the braidedconductive member 28 is rotated and the thermal radiation sourcegenerates heat, the insulation is burned off the particular region.

[0056] Insulation removal may also be accomplished by masking selectedportions of braided conductive member 28. A mask, such as a metal tubemay be placed over braided conducive member 28. Alternatively, braidedconductive member 28 may be wrapped in foil or covered with some type ofphotoresist. The mask is then removed in the areas in which insulationremoval is desired by, for example, cutting away the mask, 30 slicingthe foil, or removing the photoresist. Alternatively, a mask can beprovided that has a predetermined insulation removal pattern. Forexample, a metal tube having cutouts that, when the metal tube is placedover braided conductive member 28, exposes areas where insulation is tobe removed.

[0057]FIG. 6 illustrates how thermal radiation 52 may be applied to theouter circumferential surface 56 of a respective filament 34 thatdefines the outer circumferential surface 60 of braided conductivemember 28. As thermal radiation 52 is applied, the insulation 54 isburned off or removed from the outer circumference 56 of wire 34 tocreate a region 58 about the circumference 56 of filament 34 that has noinsulation.

[0058] The insulation 54 can also be removed in a preferential manner sothat a particular portion of the circumferential surface 56 of afilament 34 is exposed. Thus, when braided conductive member 28 isradially expanded, the stripped portions of filaments may preferentiallyface the intended direction of mapping or ablation.

[0059] With the insulation removed from the portions of filaments 34 onthe outer circumferential surface 60 of braided conductive member 28, aplurality of individual mapping and ablation channels can be created. Awire runs from each of the filaments 34 within catheter shaft 12 andcontrol handle 14 to connector portion 16. A multiplexer or switch boxmay be connected to the conductors so that each filament 34 may becontrolled individually. This function may be incorporated intocontroller 8. A number of filaments 34 may be grouped together formapping and ablation. Alternatively, each individual filament 34 can beused as a separate mapping channel for mapping individual electricalactivity within a blood vessel at a single point. Using a switch box ormultiplexer to configure the signals being received by filaments 34 orablation energy sent to filaments 34 results in an infinite number ofpossible combinations of filaments for detecting electrical activityduring mapping procedures and for applying energy during an ablationprocedure.

[0060] By controlling the amount of insulation that is removed from thefilaments 34 that comprise braided conductive member 28, the surfacearea of the braid that is in contact with a blood vessel wall can alsobe controlled. This in turn will allow control of the impedancepresented to an ablation energy generator, for example, generator 4, Inaddition, selectively removing the insulation can provide apredetermined or controllable profile of the ablation energy deliveredto the tissue.

[0061] The above description illustrates how insulation may be removedfrom a filaments 34. Alternatively, the same features and advantages canbe achieved by adding insulation to filaments 34. For example, filaments34 may be bare wire and insulation can be added to them.

[0062] Individual control of the electrical signals received fromfilaments 34 allows catheter 10 to be used for bipolar (differential orbetween filament) type mapping as well as unipolar (one filament withrespect to a reference) type mapping.

[0063] Catheter 10 may also have, as illustrated in FIGS. 2 and 3, areference electrode 13 mounted on shaft 12 so that reference electrode13 is located outside the heart during unipolar mapping operations.

[0064] Radiopaque markers can also be provided for use in electrodeorientation and identification.

[0065] One skilled in the art will appreciate all of the insulation canbe removed from filaments 34 to create a large ablation electrode.

[0066] Although a complete catheter steerable structure has beenillustrated, the invention can also be adapted so that inner tubularmember 22 is a catheter shaft, guide wire, or a hollow tubular structurefor introduction of saline, contrast media, heparin or other medicines,or introduction of guidewires, or the like.

[0067] Temperature Sensing

[0068] A temperature sensor or sensors, such as, but not limited to, oneor more thermocouples may be attached to braided conductive member 28for temperature sensing during ablation procedures. A plurality ofthermocouples may also be woven into the braided conductive member 28.An individual temperature sensor could be provided for each of thefilaments 34 that comprise braided conductive member 28. Alternatively,braided conductive member 28 can be constructed of one or moretemperature sensors themselves.

[0069]FIG. 8 illustrates braided conductive member 28 in its fullyexpanded or deployed configuration. Braided conductive member 28 forms adisk when fully expanded. In the embodiment illustrated in FIG. 8, thereare sixteen filaments 34 that make up braided conductive member 28.

[0070] Temperature monitoring or control can be incorporated intobraided conductive member 28, for example, by placing temperaturesensors (such as thermocouples, thermistors, etc.) on the expandedbraided conductive member 28 such that they are located on the distallyfacing ablative ring formed when braided conductive member 28 is in itsfully expanded configuration. “Temperature monitoring” refers totemperature reporting and display for physician interaction.“Temperature control” refers to the capability of adding an algorithm ina feedback loop to titrate power based on temperature readings from thetemperature sensors disposed on braided conductive member 28.Temperature sensors can provide a means of temperature control providedthe segment of the ablative ring associated with each sensor isindependently controllable (e.g., electrically isolated from otherregions of the mesh). For example, control can be achieved by dividingthe ablative structure into electrically independent sectors, each witha temperature sensor, or alternatively, each with a mechanism to measureimpedance in order to facilitate power titration. The ablative structuremay be divided into electrically independent sectors so as to providezone control. The provision of such sectors can be used to provide powercontrol to various sections of braided conductive member 28.

[0071] As illustrated in FIG. 8, four temperature sensors 70 areprovided on braided conductive member 28. As noted previously, since theindividual filaments 34 in braided conductive member 28 are insulatedfrom each other, a number of independent sectors may be provided. Asector may include one or more filaments 34. During ablation procedures,energy can be applied to one or more of the filaments 34 in anycombination desired depending upon the goals of the ablation procedure.A temperature sensor could be provided on each filament 34 of braidedconductive member 28 or shared among one or more filaments. In mappingapplications, one or more of the filaments 34 can be grouped togetherfor purposes of measuring electrical activity. These sectoring functionscan be provided in controller 8.

[0072]FIG. 10 illustrates a side view of braided conductive member 28including temperature sensors 70. As shown in FIG. 10, temperaturesensors 70 emerge from four holes 72. Each hole 72 is disposed in onequadrant of anchor 74. The temperature sensors 70 are bonded to theoutside edge 76 of braided conductive member 28. Temperature sensors 70may be isolated by a small piece of polyimide tubing 73 around them andthen bonded in place to the filaments. The temperature sensors 7 may bewoven and twisted into braided conductive member 28 or they can bebonded on a side-by-side or parallel manner with the filaments 34.

[0073] There are several methods of implementing electricallyindependent sectors. In one embodiment, the wires are preferablystripped of their insulative coating in the region forming the ablativering (when expanded). However, sufficient insulation may be left on thewires in order to prevent interconnection when in the expanded state.Alternatively, adjacent mesh wires can be permitted to touch in theirstripped region, but can be separated into groups by fully insulated(unstripped) wires imposed, for example, every 3 or 5 wires apart (thenumber of wires does not limit this invention), thus forming sectors ofindependently controllable zones. Each zone can have its own temperaturesensor. The wires can be “bundled” (or independently attached) toindependent outputs of an ablation energy generator. RF energy can thenbe titrated in its application to each zone by switching power on andoff (and applying power to other zones during the ‘off period’) or bymodulating voltage or current to the zone (in the case of independentcontrollers). In either case, the temperature inputs from thetemperature sensors can be used in a standard feedback algorithm tocontrol the power delivery.

[0074] Alternatively, as illustrated in FIG. 10A, braided conductivemember 28 may be used to support a ribbon-like structure which isseparated into discrete sectors. As shown in FIG. 10A, the ribbon-likestructure 81 may be, for example, a pleated copper flat wire that, asbraided conductive member 28 expands, unfolds into an annular ring. Eachof the wires 83 a-83 d lie in the same plane. Although four wires areillustrated in FIG. 10A, structure 81 may include any number of wiresdepending upon the application and desired performance. Each of wires 83a-83 d is insulated. Insulation may then be removed from each wire tocreate different sectors 85 a-85 d. Alternatively, each of wires 83 a-83d may be uninsulated and insulation may be added to create differentsectors. The different sectors provide an ablative zone comprised ofindependently controllable wires 83 a-83 d. Temperature sensors 70 maybe mounted on the individual wires, and filaments 34 may be connected torespective wires 83 a-83 d to provide independent control of energy toeach individual sector. One skilled in the art will appreciate that eachof wires 83 a-83 d can have multiple sectors formed by removinginsulation in various locations and that numerous combinations ofsectors 85 a-85 d and wires 83 a-83 d forming ribbon-like structure 81can be obtained.

[0075] Steering

[0076] Reference is now made to FIGS. 11-13 which illustrate aspects ofthe steering capabilities of the present invention. As illustrated inFIGS. 1-2, catheter 10 is capable of being steered using control handle14. In particular, FIG. 1 illustrates steering where the steering pivotor knuckle is disposed on catheter shaft 12 in a region that is distalto the braided conductive member 28.

[0077]FIG. 11 illustrates catheter 10 wherein the pivot point orsteering knuckle is disposed proximal to braided conductive member 28.

[0078]FIG. 12 illustrates catheter 10 having the capability of providingsteering knuckles both proximal and distal to braided conductive member28.

[0079] FIGS. 1-2, and 11-12 illustrate two dimensional or single planetype steering. The catheter of the present invention can also be used inconnection with a three dimensional steering mechanism. For example,using the control handle in the incorporated by reference '852 patent,the catheter can be manipulated into a three-dimensional “lasso-like”shape, particularly at the distal end of the catheter. As shown in FIG.13, the catheter can have a primary curve 80 in one plane and then asecond curve 82 in another plane at an angle to the first plane. Withthis configuration, the catheter can provide increased access todifficult to reach anatomical structures. For example, a target site fora mapping or ablation operation may be internal to a blood vessel. Thus,the increased steering capability can allow easier access into thetarget blood vessel. In addition, the additional dimension of steeringcan allow for better placement of braided conductive member 28 during anablation or mapping procedure. Catheter 10 can be inserted into a siteusing the steering capabilities provided by primary curve 80.Thereafter, using the secondary curve 82, braided conductive member 28can be tilted into another plane for better orientation or contact withthe target site.

[0080] Conductive Member Configurations And Materials

[0081] Reference is now made to FIGS. 14-17 which figures illustrateother configurations of braided conductive member 28. As has beendescribed above and will be described in more detail, braided conductivemember 28 can include from one to 300 or more filaments. The filamentsmay vary from very fine wires having small diameters or cross-sectionalareas to large wires having relatively large diameters orcross-sectional areas.

[0082]FIG. 14 illustrates the use of more than one braided conductivemember 28 as the distal end of catheter 10. As shown in FIG. 14, threebraided conductive members 28A, 28B, and 28C are provided at the distalend of catheter 10. Braided conductive members 28A, 28B, and 29C may be,in their expanded conditions, the same size or different sizes. Each ofthe braided conductive members 28A, 28B, and 28C can be expanded orcontracted independently in the manner illustrated in FIGS. 1-4 viaindependent control shafts 26A, 26B, and 26C. The use of multiplebraided conductive members provides several advantages. Rather thanhaving to estimate or guess as to the size of the blood vessel prior tostarting a mapping or ablation procedure, if braided conductive members28A, 28B, and 28C are of different expanded diameters, than sizing canbe done in vivo during a procedure. In addition, one of the braidedconductive members can be used for ablation and another of the braidedconductive members can be used for mapping. This allows for quicklychecking the effectiveness of an ablation procedure.

[0083] Reference is now made to FIGS. 15A and 15B, which figuresillustrate other shapes of braided conductive member 28. As described upto this point, braided conductive member 28 is generally symmetrical andcoaxial with respect to catheter shaft 12. However, certain anatomicalstructures may have complex three-dimensional shapes that are not easilyapproximated by a geometrically symmetrical mapping or ablationstructure. One example of this type of structure occurs at the CSostium. To successfully contact these types of anatomical structures,braided conductive member 28 can be “preformed” to a close approximationof that anatomy, and yet still be flexible enough to adapt to variationsfound in specific patients. Alternatively, braided conductive member 28can be “preformed” to a close approximation of that anatomy, and be ofsufficient strength (as by choice of materials, configuration, etc.) toforce the tissue to conform to variations found in specific patients.For example FIG. 15A illustrates braided conductive member 28 disposedabout shaft 12 in an off-center or non concentric manner. In addition,braided conductive member 28 may also be constructed so that theparameter of the braided conductive member in its expanded configurationhas a non-circular edge so as to improve tissue contact around theparameter of the braided conductive member. FIG. 15B illustrates anexample of this type of configuration where the braided conductivemember 28 is both off center or non concentric with respect to cathetershaft 12 and also, in its deployed or expanded configuration, has anasymmetric shape. The eccentricity of braided conductive member 28 withrespect to the shaft and the asymmetric deployed configurations can beproduced by providing additional structural supports in braidedconductive member 28, for example, such as by adding nitinol, ribbonwire, and so on. In addition, varying the winding pitch or individualfilament size or placement or deforming selective filaments in braidedconductive member 28 or any other means known to those skilled in theart may be used.

[0084] FIGS. 16A-16C illustrate another configuration of braidedconductive member 28 and catheter 10. As illustrated in FIGS. 16A-16C,the distal tip section of catheter 10 has been removed and braidedconductive member 28 is disposed at the distal end of catheter 10. Oneend of braided conductive member 28 is anchored to catheter shaft 12using an anchor band 90 that clamps the end 32 of braided conductivemember 28 to catheter shaft 12. The other end of braided conductivemember 28 is clamped to an activating shaft such as shaft 26 usinganother anchor band 92. FIG. 16A illustrates braided conductive member28 in its undeployed configuration. As shaft 26 is moved distally,braided conductive member 28 emerges or everts from shaft 12. As shownin FIG. 16B, braided conductive member 28 has reached its fully deployeddiameter and an annular tissue contact zone 29 can be placed against anostium or other anatomical structure. As illustrated in FIG. 16C,further distal movement of shaft 26 can be used to create a concentriclocating region 94 that can help to provide for concentric placementwithin an ostium of a pulmonary vein, for example. Concentric locatingregion 94 may be formed by selective variations in the winding densityof filaments 34 in braided conductive member 28, preferentialpredeformation of the filaments, additional eversion of braidedconductive member 28 from shaft 12, or by other means known to thoseskilled in the art.

[0085] Reference is now made to FIG. 17, which figure illustrates afurther embodiment of braided conductive member 28. As illustrated inFIG. 17, braided conductive member 28 is composed of one or severallarge wires 96 rather than a multiplicity of smaller diameter wires. Thewire or wires can be moved between the expanded and unexpanded positionsin the same manner as illustrated in FIG. 1. In addition, a region 98may be provided in which the insulation has been removed for mapping orablation procedures. The single wire or “corkscrew” configurationprovides several advantages. First, the wire or wires do not cross eachother and therefore there is only a single winding direction requiredfor manufacture. In addition, the risk of thrombogenicity may be reducedbecause there is a smaller area of the blood vessel being blocked. Inaddition, the connections between the ends of the large wire and thecontrol shafts may be simplified.

[0086] The catheter 10 of the present invention can be coated with anumber of coatings that can enhance the operating properties of braidedconductive member 28. The coatings can be applied by any of a number oftechniques and the coatings may include a wide range of polymers andother materials.

[0087] Braided conductive member 28 can be coated to reduce itscoefficient of friction, thus reducing the possibility of thrombiadhesion to the braided conductive member as well as the possibility ofvascular or atrial damage. These coatings can be combined with theinsulation on the filaments that make up braided conductive member 28,these coatings can be included in the insulation itself, or the coatingscan be applied on top of the insulation. Examples of coating materialsthat can be used to improve the lubricity of the catheter include PDslick available from Phelps Dodge Corporation, Ag, Tin, BN. Thesematerials can be applied by an ion beam assisted deposition (“IBAD”)technique developed by, for example, Amp Corporation.

[0088] Braided conductive member 28 can also be coated to increase ordecrease its thermal conduction which can improve the safety or efficacyof the braided conductive member 28. This may be achieved byincorporating thermally conductive elements into the electricalinsulation of the filaments that make up braided conductive member 28 oras an added coating to the assembly. Alternatively, thermally insulatingelements may be incorporated into the electrical insulation of thefilaments that make up braided conductive member 28 or added as acoating to the assembly. Polymer mixing, IBAD, or similar technologycould be used to add Ag, Pt, Pd, Au, Ir, Cobalt, and others into theinsulation or to coat braided conductive member 28.

[0089] Radioopaque coatings or markers can also be used to provide areference point for orientation of braided conductive member 28 whenviewed during fluoroscopic imaging. The materials that provideradiopacity including, for example, Au, Pt, Ir, and other known to thoseskilled in the art. These materials may be incorporated and used ascoatings as described above.

[0090] Antithrombogenic coatings, such as heparin and BH, can also beapplied to braided conductive member 28 to reduce thrombogenicity toprevent blood aggregation on braided conductive member 28. Thesecoatings can be applied by dipping or spraying, for example.

[0091] As noted above, the filament 34 of braided conductive member 28may be constructed of metal wire materials. These materials may be, forexample, MP35N, nitinol, or stainless steel. Filaments 34 may also becomposites of these materials in combination with a core of anothermaterial such as silver or platinum. The combination of a highlyconductive electrical core material with another material forming theshell of the wire allows the mechanical properties of the shell materialto be combined with the electrical conductivity of the core material toachieve better and/or selectable performance. The choice and percentageof core material used in combination with the choice and percentage ofshell material used can be selected based on the desired performancecharacteristics and mechanical/electrical properties desired for aparticular application.

[0092] Irrigation

[0093] It is known that for a given electrode side and tissue contactarea, the size of a lesion created by radiofrequency (RF) energy is afunction of the RF power level and the exposure time. At higher powers,however, the exposure time can be limited by an increase in impedancethat occurs when the temperature at the electrode-tissue interfaceapproaches a 100° C. One way of maintaining the temperature less than orequal to this limit is to irrigate the ablation electrode with saline toprovide convective cooling so as to control the electrode-tissueinterface temperature and thereby prevent an increase in impedance.Accordingly, irrigation of braided conductive member 28 and the tissuesite at which a lesion is to be created can be provided in the presentinvention. FIG. 18 illustrates the use of an irrigation manifold withinbraided conductive member 28. An irrigation manifold 100 is disposedalong shaft 22 inside braided conductive member 28. Irrigation manifold100 may be one or more polyimid tubes. Within braided conductive member28, the irrigation manifold splits into a number of smaller tubes 102that are woven into braided conductive member 28 along a respectivefilament 34. A series of holes 104 may be provided in each of the tubes102. These holes can be oriented in any number of ways to target aspecific site or portion of braided conductive member 28 for irrigation.Irrigation manifold 100 runs through catheter shaft 12 and may beconnected to an irrigation delivery device outside the patient used toinject an irrigation fluid, such as saline, for example, such as duringan ablation procedure.

[0094] The irrigation system can also be used to deliver a contrastfluid for verifying location or changes in vessel diameter. For example,a contrast medium may be perfused prior to ablation and then after anablation procedure to verify that there have been no changes in theblood vessel diameter. The contrast medium can also be used duringmapping procedures to verify placement of braided conductive member 28.In either ablation or mapping procedures, antithrombogenic fluids, suchas heparin can also be perfused to reduce thrombogenicity.

[0095]FIG. 19 illustrates another way of providing perfusion/irrigationin catheter 10. As illustrated in FIG. 19, the filaments 34 thatcomprise braided conductive member 28 are composed of a composite wire110. The composite wire 110 includes an electrically conductive wire 112that is used for delivering ablation energy in an ablation procedure orfor detecting electrical activity during a mapping procedure. Electricalwire 112 is contained within a lumen 114 that also contains a perfusionlumen 116. Perfusion lumen 116 is used to deliver irrigation fluid or acontrast fluid as described in connection with FIG. 18. Once braidedconductive member 28 has been constructed with composite wire 110, theinsulation 118 surrounding wire filament 112 can be stripped away toform an electrode surface. Holes can then be provided into perfusionlumen 116 to then allow perfusion at targeted sites along the electrodesurface. As with the embodiment illustrated in FIG. 18, the perfusionlumens can be connected together to form a manifold which manifold canthen be connected to, for example, perfusion tube 120 and connected to afluid delivery device.

[0096] Shrouds

[0097] The use of a shroud or shrouds to cover at least a portion ofbraided conductive member 28 can be beneficial in several ways. Theshroud can add protection to braided conductive member 28 duringinsertion and removal of catheter 10. A shroud can also be used to formor shape braided conductive member 28 when in its deployed state.Shrouds may also reduce the risk of thrombi formation on braidedconductive member 28 by reducing the area of filament and the number offilament crossings exposed to blood contact. This can be particularlybeneficial at the ends 30 and 32 of braided conductive member 28. Thedensity of filaments at ends 30 and 32 is greatest and the ends cantherefore be prone to blood aggregation. The shrouds can be composed oflatex balloon material or any material that would be resistant tothrombi formation durable enough to survive insertion through anintroducer system, and would not reduce the mobility of braidedconductive member 28. The shrouds can also be composed of an RFtransparent material that would allow RF energy to pass through theshroud. If an RF transparent material is used, complete encapsulation ofbraided conductive member 28 is possible.

[0098] A shroud or shrouds may also be useful when irrigation orperfusion is used, since the shrouds can act to direct irrigation orcontrast fluid to a target region.

[0099] FIGS. 20A-20E illustrate various examples of shrouds that may beused in the present invention. FIG. 20A illustrates shrouds 130 and 132disposed over end regions 31 and 33, respectively, of braided conductivemember 28. This configuration can be useful in preventing coagulation ofblood at the ends of braided conductive member 28. FIG. 20B illustratesshrouds 130 and 132 used in conjunction with an internal shroud 134contained inside braided conductive member 28. In addition to preventingblood coagulation in regions 31 and 32, the embodiment illustrated inFIG. 20B also prevents blood from entering braided conductive member 28.

[0100]FIG. 20C illustrates shrouds 130 and 132 being used to direct andirrigation fluid or contrast medium along the circumferential edge ofbraided conductive member 28. In the embodiment illustrated in FIG. 20C,perfusion can be provided as illustrated in FIGS. 18 and 19.

[0101]FIG. 20D illustrates the use of an external shroud that coversbraided conductive member 28. Shroud 136 completely encases braidedconductive member 28 and thereby eliminates blood contact with braidedconductive member 28. Shroud 136 may be constructed of a flexible yetablation-energy transparent material so that, when used in an ablationprocedure, braided conductive member 28 can still deliver energy to atargeted ablation site.

[0102]FIG. 20E also illustrates an external shroud 137 encasing braidedconductive member 28. Shroud 137 may also be constructed of a flexibleyet ablation-energy transparent material. Openings 139 may be providedin shroud 137 to allow the portions of braided conductive member 28 thatare exposed by the opening to come into contact with tissue. Openings139 may be elliptical, circular, circumferential, etc.

[0103] Guiding Sheaths

[0104] There may be times during ablation or mapping procedures whencatheter 10 is passing through difficult or tortuous vasculature. Duringthese times, it may be helpful to have a guiding sheath through which topass catheter 10 so as to allow easier passage through the patient'svasculature.

[0105]FIG. 21 illustrates one example of a guiding sheath that may beused in connection with catheter 10. As illustrated in FIG. 21, theguiding sheath 140 includes a longitudinal member 142. Longitudinalmember 142 may be constructed of a material rigid enough to be pushednext to catheter shaft 12 as the catheter is threaded through thevasiculature. In one example, longitudinal member 142 may be stainlesssteel. Longitudinal member 142 is attached to a sheath 144 disposed atthe distal end 146 of longitudinal member 142. The split sheath 144 mayhave one or more predetermined curves 148 that are compatible with theshapes of particular blood vessels (arteries or veins) that catheter 10needs to pass through. Split sheath 144 may extend proximally alonglongitudinal member 142. For example, sheath 144 and longitudinal member142 may be bonded together for a length of up to 20 or 30 centimeters toallow easier passage through the patient's blood vessels. Sheath 144includes a predetermined region 150 that extends longitudinally alongsheath 144. Region 150 may be, for example, a seam, that allows sheath144 to be split open so that the guiding sheath 140 can be pulled backand peeled off catheter shaft 12 in order to remove the sheath.

[0106] In another embodiment, longitudinal member 142 may be a hypotubeor the like having an opening 152 at distal end 146 that communicateswith the interior of sheath 144. In this embodiment, longitudinal member142 can be used to inject irrigation fluid such as saline or a contrastmedium for purposes of cooling, flushing, or visualization.

[0107] Methods Of Use

[0108] Reference is now made to FIGS. 22, 23, and 24, which figuresillustrate how the catheter of the present invention may be used inendocardial and epicardial applications.

[0109] Referring to FIG. 22, this figure illustrates an endocardialablation procedure. In this procedure, catheter shaft 12 is introducedinto a patient's heart 150. Appropriate imaging guidance (direct visualassessment, camera port, fluoroscopy, echocardiographic, magneticresonance, etc.) can be used. FIG. 22 in particular illustrates cathetershaft 12 being placed in the left atrium of the patient's heart. Oncecatheter shaft 12 reaches the patient's left atrium, it may then beintroduced through an ostium 152 of a pulmonary vein 154. Asillustrated, braided conductive member 28 is then expanded to itsdeployed position, where, in the illustrated embodiment, braidedconductive member 28 forms a disk. Catheter shaft 12 then advancedfurther into pulmonary vein 154 until the distal side 156 of braidedconductive member 28 makes contact with the ostium of pulmonary vein154. External pressure may be applied along catheter shaft 12 to achievethe desired level of contact of braided conductive member 28 with theostium tissue. Energy is then applied to the ostium tissue 152 incontact with braided conductive member 28 to create an annular lesion ator near the ostium. The energy used may be RF (radiofrequency), DC,microwave, ultrasonic, cryothermal, optical, etc.

[0110] Reference is now made to FIG. 23, which figure illustrates anepicardial ablation procedure. As illustrated in FIG. 23, catheter shaft12 is introduced into a patient's thoracic cavity and directed topulmonary vein 154. Catheter 10 may be introduced through a trocar portor intraoperatively during open chest surgery Using a steeringmechanism, preformed shape, or other means by which to make contactbetween braided conductive member 128 and the outer surface 158 ofpulmonary vein 154, braided conductive member 28 is brought into contactwith the outer surface 158 of pulmonary vein 154. Appropriate imagingguidance (direct visual assessment, camera port, fluoroscopy,echocardiographic, magnetic resonance, etc.) can be used. As illustratedin FIG. 23, in this procedure, braided conductive member 28 remains inits undeployed or unexpanded condition. External pressure maybe appliedto achieve contact between braided conductive member 28 with pulmonaryvein 154. Once the desired contact with the outer surface 158 ofpulmonary vein 154 is attained, ablation energy is applied to surface158 via braided conductive member 28 using, for example, RF, DC,ultrasound, microwave, cryothermal, or optical energy. Thereafter,braided conductive member 28 may be moved around the circumference ofpulmonary vein 154, and the ablation procedure repeated. This proceduremay be used to create, for example, an annular lesion at or near theostium.

[0111] Use of the illustrated endocardial or epicardial procedures maybe easier and faster than using a single “point” electrode since acomplete annular lesion may be created in one application of RF energy.

[0112] Reference is now made to FIG. 24 which figure illustrates anendocardial mapping procedure. In the procedure illustrated in FIG. 24,catheter shaft 12 is introduced into pulmonary vein 154 in the mannerdescribed in connection with FIG. 22. Once braided conductive 28 hasreached a desired location within pulmonary vein 154, braided conductivemember 28 is expanded as described in connection with, for example,FIGS. 2-5 until filaments 34 contact the inner wall 160 of pulmonaryvein 154. Thereafter, electrical activity within pulmonary vein 154 maybe detected, measured, and recorded by an external device connected tothe filaments 34 of braided conductive member 28.

[0113] Access to the patient's heart can be accomplished viapercutaneous, vascular, surgical (e.g. open-chest surgery), ortransthoracic approaches for either endocardial or epicardial mappingand/or mapping and ablation procedures.

[0114] The present invention is thus able to provide anelectrophysiology catheter capable of mapping and/or mapping andablation operations. In addition, the catheter of the invention may beused to provide high density maps of a tissue region becauseelectrocardiograms may be obtained from individual filaments 34 inbraided conductive member 28 in either a bipolar or unipolar mode.

[0115] Furthermore, the shape of the electrode region can be adjusted bycontrolling the radial expansion of braided conductive member 28 so asto improve conformity with the patient's tissue or to provide a desiredmapping or ablation profile. Alternatively, braided conductive member 28may be fabricated of a material of sufficient flexural strength so thatthe tissue is preferentially conformed to match the expanded orpartially expanded shape of the braided conductive member 28.

[0116] The catheter of the present invention may be used for mappingprocedures, ablation procedures, and temperature measurement and controlon the distal and/or proximal facing sides of braided conductive member28 in its fully expanded positions as illustrated in, for example,FIG. 1. In addition, the catheter of the present invention can be usedto perform “radial” mapping procedures, ablation procedures, andtemperature measurement and control. That is, the outer circumferentialedge 76, illustrated, for example, in FIG. 8, can be applied against aninner circumferential surface of a blood vessel.

[0117] Furthermore, being able to use the same catheter for both mappingand ablation procedures has the potential to reduce procedure time andreduce X-ray exposure.

[0118] The ability to expand braided conductive member 28 in an arteryor vein against a tissue structure such as a freewall or ostium canprovide good contact pressure for multiple electrodes and can provide ananatomical anchor for stability. Temperature sensors can be positioneddefinitively against the endocardium to provide good thermal conductionto the tissue. Lesions can be selectively produced at various sectionsaround the circumference of braided conductive member 28 without havingto reposition catheter 10. This can provide more accurate lesionplacement within the artery or vein.

[0119] Braided conductive member 28, in its radially expanded positionas illustrated in particular in FIGS. 1 and 8 is advantageous because,in these embodiments, it does not block the blood vessel during amapping or ablation procedure, but allows blood flow through the braidedconductive member thus allowing for longer mapping and/or ablationtimes, which can potentially improve accuracy of mapping and efficacy oflesion creation.

[0120] Having thus described at least one illustrative embodiment of theinvention, various alterations, modifications, and improvements willreadily occur to those skilled in the art. Such alterations,modifications, and improvements are intended to be within the spirit andscope of the invention. Accordingly, the foregoing description is by wayof example only and is not intended as limiting. The invention islimited only as defined in the following claims and the equivalentsthereto.

What is claimed is:
 1. A medical device, comprising: a catheter having a braided conductive member at a distal end thereof; means for expanding the braided conductive member from an undeployed to a deployed position; and means for applying energy via the braided conductive member to a blood vessel.
 2. The medical device of claim 1, further comprising means for irrigating the braided conductive member.
 3. The medical device of claim 1, further comprising at least one reference electrode disposed on a shaft of the catheter.
 4. The medical device of claim 1, further comprising means for controlling the energy supplied to the braided conductive member.
 5. The medical device of claim 1, further comprising means for covering at least a portion of the braided conductive member when the braided conductive member is in the deployed position.
 6. The medical device of claim 1, wherein at least a portion of the braided conductive member has a coating applied thereto.
 7. The medical device of claim 1, further comprising means for measuring temperature.
 8. The medical device of claim 1, further comprising means for steering the catheter.
 9. The medical device of claim 1, wherein the braided conductive member is a wire mesh.
 10. A method for treating cardiac arrhythmia, comprising the steps of: introducing a catheter having a braided conductive member at a distal end thereof into a blood vessel; expanding the braided conductive member at a selected location in the blood vessel so that the braided conductive member contacts a wall of the blood vessel; and applying energy to the wall of the blood vessel via the braided conductive member to create a lesion in the blood vessel.
 11. The method of claim 10, wherein the braided conductive member is a wire mesh.
 12. A method for treating cardiac arrhythmia, comprising the steps of: introducing a catheter into a thoracic cavity of a patient, the catheter having a braided conductive member at a distal end thereof; contacting an exterior wall of a blood vessel in a vicinity of an ostium with the braided conductive member; and applying energy to the blood vessel via the braided conductive member to create a lesion on the exterior wall of the blood vessel.
 13. The method of claim 12, wherein the braided conductive member is a wire mesh. 